Process for the decaffeination of coffee



Patented May 9, 1939 PATENT OFFICE PROCESS FOR Tlg DECAFFEINATION OF FFEE Walter C. Hasslhorn and Joseph John Thompson, Battle Creek, Mich, assignors t'o Kellogg Company, Battle Creek, Mich a corporation of Delaware Application February 12, 1938, Serial No. 190,344

3 Claims.

This invention relates to a process and apparatus for the decafieination of coffee. v

The object of the invention is to provide a decaifeination process which is applicable for use on grades of cofiee to which, so far as we are aware, no previously existing process has-been capable of successful application or use.

An apparatus suitable for carrying out the process of the present-invention is illustrated in the accompanying drawings in which reference numerals indicate corresponding parts in the different figures-of the drawings.

'In the drawings: Figure 1 is a diagrammatical illustration of the necessary equipment.

Figure 2 is across section showing the extraction drum in vertical section.

Referring to Figure 1 of the drawings, the reference numeral l-indicates a'downward chute by which the green coffee beans are introduced into an extraction drum 2.

After the charge of green coffee beans has been introduced into the extraction drum 2, a valve 3 is closed.

The detailed construction of the drum 2 is illustrated in Figure 2 of the drawings, in which the chute I is threaded into the cover'plate 4 which is suitably fixed to the top of the drum 2. Said drum 2 is lined completely with Monel metal 5 so as to resist the chemical action of the solvent during the decafieination process. Said drum 2 contains a chamber 6 made either of wood or metal and separated from 5 by approximately 1" space.

Within the lower portion of the extraction drum 2 is a funnel-shaped screen 1 having an opening 8 at its center, which communicates with an outlet pipe 9 closed at its bottom by a fluid tight valve l held tightly in place by the handwheel ll.

At the top portion of the extraction drum 2 4 is a perforated Monel metal screen l2 connected "to downward chute l by a perforated cylinder l3.

(Figure #1.) Wateris supplied to the extraction drum 2 through the water supply pipe I and is discharged through line l5.

Steam'is supplied to drum 2 through a steam pipe I which connects with any suitable source of steam'supply and passes to the top of the extraction drum 2 and is discharged throughthe vacuumline ll. 1 v

Any suitable caii'eine solvent, such as .trichlorethylene, is contained in the solvent reservoir l8, from which it supplies the extraction drum 2 and first cleaned with a blower to remove as much as possible the dirt and extraneous material.

The green coffee beans are then supplied to the 10 extraction drum through a screw conveyor and pipe I. The moisture content of the beans, when fed into the extraction drum 2, is about 10%.

The beans lie in the drum 2 and are supported by the perforated screen I. The drum 2 is filled approximately three quarters full of the cold unheated beans.

Cold water is then fed into the extraction drum 2 through the pipe ll .until the beans are just covered by the water and immersed therein.

The beans are permitted to stand in the cold water at a temperature of approximately 68 degrees Fahr. for approximately one hour. This immersion'of the beans in relatively cold water serves, not only to wash the outside surface of the beans, but causes'what may be called a surface absorption of water, which increases the water content of the beans from about to around 21% or 22%, but the bean is not as yet uniformly permeated with water.

After the drum 2 has been filled with cold water to the level of the cofl'ee beans therein and after the beans have been permitted to stand in the water for approximately one hour, as previously Fahr. and maintained at that low a temperature for about four hours. 1 This steam treatment of the coffee beans leaves them with a water content of from 20% to 22%,, which is distributed more or less evenly through-' out the bean.

The steam is then shut off andv the bottom pipe 9 is opened to drain of! any accumuiated moisture.

The solvent from the reservoir" is then passed proximately 140 degrees Fahr.

through the pump 2|, pipes 22, 23, 24, 25, I5, valve 29 and pipe 26 into-the solvent vaporizer l9. When drum 2 and solvent vaporizer I! have sufllcient solvent, the reservoir supply is discontinued. The solvent passes through a hot water heater 30 whereby the solvent is heated to ap- The hot solvent passes upward through the unagitated mass of coffee beans which have been swollen under the cold water washing and subsequent steam treatment.

The solvent carrying the extracted matter, which includes caffeine, coflee wax-and other extractive matter and impurities leaves the extraction drum at the top through the exit pipe 26 and passes into the upper portion of the solvent 'vaporizer l9, wherein -the solvent is suitably heated and driven off as vapor through the pipe 3| to the condenser 32, from which the condensed solvent. passes back by way of .pipes 33,

24, 25, I5 and 26, valves 28 and 21 being "closed.

- The solvent is circulated from solvent vaporizer 19 through 'solvent warmer 30, extraction drum 2, for approximately thirty-two hours at a temperature of approximately 140 degrees Fahr.

By this time the solvent is clear because practically all of the caffeine has been extracted from the green'cofl'ee. a The solvent remaining in the extraction drum 2 is now drained back into the solvent reservoir l8 by pipe IS with valve 21 open.

The green coffee in the extraction drum 2 is now of a moisture content of 18%.

After all the solvent that is capable of being drained ofi of the coffee beans has beendrained back to the solvent reservoir l8, the remainder of the solvent which is still contained within the washed coflee beans is driven from the beans by again passing steam through the extraction drum 2 at a temperature of around 160 degrees to 170 degrees Fahr. This is continued for approximately twenty hours.

Where the process iscarried out with a high grade coiIee bean having no constituent capable of producing disagreeable flavor or odor, it is only necessary to use steam alone in steaming out the solvent, but where a lower grade of coffee bean is employed, such as an African bean, we have discovered that it is necessary to supply air to the extraction drum 2 along with the steam.

Air is supplied to the steam line- IS in any suitable manner, the air may be letin either under the Venturi principle vor it may be compressed and thus fitted to the steam line on the supercharger principle.

In using African coffee, approximately 13.6

cubic feet of air per hour in conjunction with 52.7 cubic feet per hour of steam are supplied.

The air tends to-oxidize someof the. undesirable compounds present in the African and simi+ lar grades of coffee.

After the steam and air treatment is discontinued, any liquid remaining in the extraction drum .2 is first drawn off through the outlet 9, then the decafieinated coffee is removed from the extraction drum 2 through outlet 9, and thereafter it is sent to the roasting, grinding and packing mechanism.

What is claimed as new is:

l. A method of extracting caffeine from coffee which consists in subjecting the coffee beans in a confined space to the action of relatively cold water to produce a surface absorption of water, withdrawing the water and subjecting the'beans to steam thereby evenly distributing the water content throughout the beans, draining off the moisture from the beans, subjecting the beans without agitation to an upward circulation of hot solvent, withdrawing all of the solvent except that contained in the beans and subjecting the coffee beans again to the action of steam to remove the remaining solvent.

2. A method of extracting caffeine from cofiee' which comprises subjecting the coffee beans to the action of relatively cold water to produce a surface absorption of water, withdrawing the water and subjecting the beans to steam thereby evenly distributing the water content throughout the beans, draining off the moisture from the beans, subjecting the beans to extraction with a hot solvent, withdrawing all of the solvent except that contained within the beans and subjecting the coffee beans to the combining action of steam and air to remove the remaining solvent.

3. A method of extracting-caffeine from cofieeaction of steam to remove the remaining solvent.

- WALTER C. HASSELHORN.

JOSEPH JOHN THOMPSON. 

